1,3-hexadiene-5-one and a method for producing same



Patented Nov. 18, 1941 UNITED STATES 1,3-HEXADIENE--ONE AND A METHOD FOR PRODUCING SAME Albert Smith Carter, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application July 22, 1939, Serial No. 285,859

9 Claims.

This invention relates to 1,3-hexadiene-5-one and its preparation.

This application is a continuation-in-part of copending application Serial No. 155,923, filed July 27, 1937.

In U. S. Patent No. 1,811,959, Nieuwland describes a new process by which acetylene may be polymerized to non-benzenoid polymers of acetylene. AInOIlg the polymers of acetylene so obtained is divinylacetylene, first disclosed in the above patent. The process described in this patent, as well as in later patents of others, gives a divinylacetylene which is essentially constant boiling and which was thought to be a homogeneous substance.

If this divinylacetylene is tested for the presence of acetylenic hydrogen, however, positive results are obtained which indicate the presence of small amounts of a material other than divinylacetylene. The amounts of this other material vary with variations in the broad Nieuwland process and range from about 4% to about 10% by weight of the divinylacetylene even after extensive fractional distillation. This other material has been found to be heXadiene-L3-yne-5, an isomer of divinylacetylene, having the structural formula CH2=CHCH=CHCECH. There is thus a characteristic difference between divinylacetylene and ethinylbutadiene in that the ethinylbutadiene contains a CECH group whereas divinylacetylene does not. Heretofore, ethi-nylbutadiene has not been extensively studied and many of its derivatives are unknown.

It is an object of this invention to provide new chemical compounds. A further object is to discover new derivatives of ethinylbutadiene and processes for their preparation. A still further object is toobtain 1,3-heXadiene-5-one and to discover a method for its preparation.

These objects have been accomplished by reacting ethinylbutadiene with other chemical compounds and with elements. More particularly 1,3-hexadiene-5-one has been made by reacting ethinylbutadiene with an aqueous solution of sulfuric acid containing mercury sulfate.

Ethinylbutadiene may be obtained by the polymerization of acetylene according to known processes, as, for example, those disclosed in U. S. Patents 1,811,959 and 1,876,857. When so obtained, it is mixed with other acetylene polymers and is difiicult to separate from its isomer, divinylacetylene. However, this separation can be accomplished by bringing a mixture of divinylacetylene and ethinylbutadiene into contact with a solution of a salt of cuprous copper, silver or mercury, which solution is more alkaline than about pH 6.9 or into contact with an aqueous sulfuric acid solution of mercuric sulfate, whereby the ethinylbutadiene is converted into a derivative which is readily separated from the divinylacetylene. In each case, the metal salt reacts with the CECH group in the ethinylbutadiene, although as pointed out more fully below, the mercuric sulfate derivative formed in the aqueous sulfuric acid solution is unstable and decomposes almost immediately into another compound.

The metal salt in the substantially neutral or alkaline solution is dissolved in a solvent in which the salt of ethinylbutadiene formed with the metal of the metal salt is insoluble so that when the ethinylbutadiene is brought into contact with the substantially neutral or alkaline metal salt solution a metal derivative of the ethinylbutadiene is precipitated. Thi derivative may be separated very easily from the divinylacetylene and may be further treated with alkali cyanides or dilute acids to regenerate and recover the ethinylbutadiene. Preferably, the solvent in the metal salt solution is water but it may also be another liquid having the requisite property, such as an alcohol.

When the sulfuric acid-mercuric sulfate solution is used, the ethinylbutadiene adds water forming a ketone and the ketone is then readily separated from the divinylacetylene which remains unreacted. This latter method is applicable to the making of the ketone, 1,3-hexadiene-5-one, directly from a mixture of divinylacetylene and ethinylbutadiene and is also suitable for making the ketone from pure ethinylbutadiene.

Ethinylbutadiene obtainable from its metal salts, as indicated above, by treating the metal salts with alkali cyanides or dilute acids, is a volatile liquid, which upon analysis is found to have the composition CsHs. It is thus isomeric with divinylacetylene. Reaction of this hydrocarbon with maleic anhydride, as is more fully described hereinafter, shows that it contains a conjugated system of double bonds. This, together with the fact that it has an acetylenic hydrogen, limits the choice of formulas to CH2=CH-CH=CHCECH and OH2=CH-O=CH1 OECH The behavior of the maleic anhydride addition product indicates that the second of these formulas is quite improbable for stereochemical reasons. The isomer of divinylacetylene is therefore hexadienel,3-yne-5 or ethinylbutadiene.

Ethinylbutadiene is a volatile colorless liquid which polymerizes to a viscous liquid, then to a hard solid when exposed to air. It is very sensitive to oxygen and light, rapidly becoming yellow. It can be stabilized by addition of small amounts of the usual antioxidants.

Divinylacetylene purified by removal of ethinylbutadiene no longer shows the presence of. acetylenic hydrogen. It is then much less sensitive to light, remaining (when stabilized) water-white for more than two months, as contrasted with ordinary divinylacetylene which rapidly becomes yellow under the same conditions. The polymers derived from pure divinylacetylene show an improved stability towards light.

Table I shows some of the physical properties of pure divinylacetylene and pure ethinylbutadiene.

The product formed when ethinylbutadiene is reacted with maleic anhydride is ethinyl-S-tetrahydro-l,2,3,6,-phthalic acid which may readily be reduced to ethyl 3 hexahydrophthalic acid. With hydrogen chloride in the presence of cuprous chloride ethinylbutadiene reacts to form a polymerizable liquid having the composition CsH7C1.

The invention will be better understood by consideration of the following examples, which are intended as illustrations only, however, and are thus not intended to be construed as limitations. Throughout these examples the parts are given by weight unless otherwise indicated and as in the remainder of the specification and claims the temperatures are expressed as C.

'XAMPLE 1 Isolation of ethinyibutadiene Seven hundred and ninety parts of a mixture of ethinylbutadiene and divinylacetylene (the fraction boiling from 48 to 52 at 250 mm.) was stirred for 30 minutes with a solution made by dissolving 100 parts of CuzClz in 300 parts of concentrated NHiOl-I and 1&0 parts of water and, while still warm, adding parts of hydroxylamine hydrochloride which reduced most of the cupric copper present. A heavy orange-yellow precipitate of the cuprous acetylide formed and became suspended for the most part in the divinylacetylene layer. The major portion of the divinylacetylene was then distilled oh at 100 mm., the

temperature of the mixture bein kept below 40. The lumps of the copper precipitate were then broken up and dispersed by adding more ammonia and water and the distillation was continued at 30 mm. until water-insoluble material ceased to be condensed in a cold trap in the system. An additional 160 parts of water was then distilled to assure the complete removal of divinylacetylene. The orange precipitate was then filtered and Washed with dilute ammonia, then ethanol containing a little ammonia. To further assure the removal of divinylacetylene, the precipitate was suspended again in ethanol, washed and air-dried. Ninety-five parts of product were obtained, corresponding to 6.7% of isomer in the divinylacetylene.

The precipitate, which was not wet by water, was suspended in water containing a wetting agent, treated with ice parts of sodium cyanide and steam distilled. Thirty five parts of ethinylbutadiene (4.4% of the crude mixture of ethinylbutadiene and divinylacetylene came over rapidly, followed by 3 parts of a much less volatile liquid which was collected separately. The ethinylbutadiene was stabilized with thiodiphenylamine, dried with MgSO4 and distilled at 250 mm. thru a short fraotionating column. After collecting foreshots amounting to 4 parts a main fraction of 15 parts was collected. Both came over at 51. There was considerable polymerization during distillation.

AnaZysis.-Calcd. for CsHs: C, 92.25; H, 7.75. Found C, 92.54; H, 8.13.

The physical constants listed in the table above were determined on samples of ethinylbutadiene and divinylace'tylene separated in the manner described and redistilled with special care at reduced pressure in a C02 atmosphere immediately before use.

The slightly volatile material obtained after the ethinylbutadiene had come over in the distillation of the crude copper acetylide with sodium cyanide was collected from several runs, dried and distilled at 3 mm. Almost all came over at as a colorless liquid of faint aromatic odor. It was very unsaturated toward bromine and gave a heavy precipitate with ammoniacal silver nitrate. N 1): 1.5272; (Z 4 0.9327. This proved to be a dimer.

AnaZysis.-Calcd. for Cml-liz: C, 92.25; H, 7.75. Found: C, 91.81; H, 7.69.

EXAMPLE 2 Polymerization of ethinylbutadiene A sample of ethinylbutadiene (without stabilizer) standing exposed to air for 6 days was not visibly altered except for the formation of a deep red-brown color. Heating for '7 hours on a steam bath increased the viscosity without causing gelation. On standing 6 days more at room temperature, the liquid gradually thickened and finally formed a soft gel similar to that obtained from divinylacetylene but much darker.

It gradually became hard and brittle. Films closely resembling those obtainable from the synthetic drying oil described in Collins U. S. Patent 1,812,849 were obtained when ethinylbutadiene, polymerized to the viscous stage, was poured into ethanol, the precipitate dissolved in benzene and the solution allowed to dry on a glass plate.

EXAMPLE 3 Addition of hydrogen chloride to ethinylbutadiene Seven and eight tenths parts of ethinylbutadiene was shaken with 17.5 parts of 37% HCl containing 2.5 parts of C112C12, cooling in iceto take up the heat of reaction. After standing for 1 hour at room temperature, the resulting emulsion was shaken with ammonium chloride solution, then with water, to remove most of the CuzClz and HCl, and was then distilled with steam. lhe non-aqueous distillate was shaken with ammoniacal CuzClz solution to remove the unchanged ethinylbutadiene and was then washed with water, dried and distilled in vacuo. The principal fraction (2 parts) boiling at 5 56 at 50 mm. pressure, was a colorless liquid.

AnaZysz's.Calcd. for CeHiCli C, 62.87; H, 6.17. Found C, 62.63; H, 5.91.

It polymerized rapidly on exposure to air, becoming quite viscous in 3 days. It gradually became a soft, tacky, brownish solid, and after one month had definite elastic properties. When exposed in thin films, it was hard and brittle.

EXAMPLE 4 Ethtrtylbutadz'ene and maleic anhydride Nineteen and five-tenths parts of ethinylbutadiene and 24.5 parts of maleio anhydride were heated for four hours at 75 in a closed flask. The resulting viscous liquid was poured into ice water containing a slight excess of sodium hydroxide and the small insoluble residue collected with ether. On acidifying the alkaline solution, a brown, sticky precipitate separated, followed by four parts of long white needles which were shown to be sodium acid maleate. The acid mother liquor on exhaustive extraction with ether gave 18 parts of crystalline material which yielded 7.7 parts of short prisms (melting point 148) when recrystallized from water. The material was recrystallized for analysis from ethyl acetate, giving long prisms melting at 147.

AnaZ' sis.Calcd. for 010111004: C, 61.82; H, 5.20. Found: C, 61.62; H, 5.21. Neutralization equivalent found, 103.7. Calcd. for the dibasic acid, 97.0.

Hydrogenation of the maleic anhydride additz'on product Four and eighty-five hundredths parts of the addition product in 20 parts of ethanol was hydrogenated at pounds pressure with 0.05 part of PtOZ catalyst. Hydrogen was absorbed in an amount equivalent to 2.7 moles per mole of acid. The colorless syrup which remained on evaporating the solvent partly crystallized on standing and gave 4 parts of crystalline material, melting point 110, when recrystallized from 50% ethanol. This was recrystallized for analysis by dissolving in acetic acid and diluting with water. The crystals melted at 114.

Analysis.-Calcd. for C1oH10O42 C, 59.97; H, 8.06. Neutralization equivalent, 100.1 (dibasic). Found: C, 60.39; H, 7.95. Neutralization equivalent, 104.7.

Anhydride and anilz'de of hydrogenated addition product One and five-tenths parts of the hydrogenated acid was heated at 2 mm. pressure slightly above its melting point, water was evolved and at a higher temperature the anhydride distilled almost completely as a colorless liquid, N D: 1.4825. On exposure to moist air, it was reconverted to the acid.

The anhydride, stirred with a slight excess of aniline, gave a crystalline mass which, when recrystallized from ethanol, gave flat, shiny needles melting at l9l-193.

AnaZysz's.--Calcd. for C1sH2103NI C, 69.77; H, 7.70. Found: C, 69.46; H, 7.39.

EXAMPLE 5 Cuprous salt of ethinylbutadiene This compound was insoluble in boiling acetone, boiling ethanol, and boiling benzene. It decomposed with a flash when touched with a drop of concentrated nitric acid. When warmed with sodium cyanide solution or dilute nitric acid, it gave a pronounced odor of ethinylbutadiene.

Analysis.-Calcd. for CuCeH5: Cu, 46.21. Found: Cu, 44.72, 45.36.

EXAMPLE 6 Silver salt of ethinylbutadiene A stream of nitrogen was passed thru ethinylbutadiene and then into a solution of silver nitrate in ethanol to which had been added enough ammonia to dissolve the silver oxide precipitate. A fine white crystalline precipitate of the silver derivative was formed at once. This was filtered and washed with ethanol, then airdried. When dropped in small quantities upon the melting point block, it turned black at temperatures between and at 155 it melted and. almost immediately decomposed with a flash, while above 155 it decomposed instantaneously without melting.

It was insoluble in boiling acetone, boiling benzene, boiling ethanol, and in concentrated ammonia. It dissolved readily on warming with sodium cyanide solution or dilute nitric acid, giving a pronounced odor of ethinylbutadiene.

Analysis.-Calcd. for AgCeHsZ C, 38.93; H, 2.73. Found: C, 38.67; H, 2.83.

Example 7 M ercury salt of ethinylbutadiene The reagent consisted of 132 parts of mercuric chloride and 326 parts of potassium iodide dissolved in 326 parts of water and made alkaline with 275 parts of 10% sodium hydroxide. This was shaken for 14 hours with parts of ethanol and 500 parts of crude divinylacetylene. The precipitate of mercury salt, after Washing with ethanol, and air drying, weighed 85 parts. A portion crystallized from acetone gave a white product melting between and on a melting point block and decomposing above 175.

AnaZysz's.--Calcd. for Hg (CsH5)2. C, 40.60; H, 2.84. Found: C, 40.64; H, 2.73.

When ethinylbutadiene is to be precipitated in the form of one of its metal salts, it is preferable to effect the precipitation in an aqueous alkaline solution having a pH which is substantially on the alkaline side. As indicated above, a slightly acid pH does not render the process inoperable, although a strongly acid pH does have such a tendency. As will be observed from the above examples, a suitable alkalinity may be produced by the incorporation of a basic substance such as the ammonium hydroxide used with cuprous chloride.

The precipitation of ethinylbutadiene in the form of its metal salts may be carried out, as is apparent from the above, in the presence or absence of divinyl-acetylene. Generally, the salt forms at once at ordinary temperature, although when a mercury salt is employed as the precipitant, it is advisable to agitate the reaction mixture for a considerable period to obtain maximum yields. Preferably, the metal salt which is to react with the ethinylbutadiene is present in molecular excess over the ethinylbutadiene. After its formation, the salt of ethinylbutadiene may be separated and purified as desired. Any divinylacetylene present may be distilled off,

preferably at subatmospheric pressure and recovered.

In recovering the ethinylbutadiene from its metal salts, the presence of a wetting agent during the treatment with dilute acids or alkali cyanides will be found to be beneficial. Preferably, also the acid or cyanide will be added in substantial molecular excess to promote maximum recovery. Suitable dilute acids to be used in effecting the regeneration of the ethinylbutadiene include dilute nitric, dilute sulfuric, dilute phosphoric, and dilute hydrochloric acids. Cyanides capable of decomposing the metal salts of ethinylbutadiene are, for example, potassium cyanide and sodium cyanide.

Ethinylbutadiene is readily separated after the treatment with cyanides or dilute acids by either steam distillation or by solvent extraction. It may be further purified by fractional distillation. It should be noted, however, that the ethinylbutadiene is preferably stabilized against polymerization during distillation by the incorporation of an antioxidant.

A physical method rather than a chemical one may be adopted for extracting substantial portions of the ethinylbutadiene present in crude divinylacetylene. This method is based on the different solubilities of ethinylbutadiene and divinylacetylene in dilute ethanol, although other solvents may be used. Reasonably pure ethinylbutadiene may be obtained in fair yields by means of a series of systematic extractions which do not involve a great number of steps. Suitable solvents are those which have a substantially different distribution co-emcient for the two hydrocarbons. The principle of this method is illustrated in Eample 8.

EXAMPLE 8 Extraction of ethinylbutadiene from crude divinylacetylene One hundred parts of crude divinylacetylene containing 10.2% of ethinylbutadiene was extracted with successive 100 part portions of 70% ethanol. The total hydrocarbon present in alcoholic solution was determined roughly by diluting and washing with ice water and drying and weighing the insoluble residue. Ethinylbutadiene was determined by precipitation with a solution of silver nitrate in ethanol. The results are listed in Table II below.

Table I I Successive extraction of 100 parts of crude DVA containing 10.2% of isomer with 100 part portions of 70% ethanol Resi- Extraet No. 1 2 3 due Weight of extract 84 136 166 12 Hydrocarbons. 12 22 26 67 Isorner 2. 2 2. 9 2. 8 5. 9 Weight hydrocarbons" 10. l 30 43 8. Weight isomer 1. 82 3. 9 4. 7 0.7 Isomer in extracted H. (lpercenh 18.0 13. l 9. 2 *8. 8 Original H. C. extractednwdmn. 10.1 30 43 *8. 0 Original isomer extractedudonu 17.6 38 46 *6. 9

example, methanol, ethanol, and propanol, may be used. This method is particularly preferred where it is desired to recover the ethinylbutadiene.

The following examples illustrate the preparation of the ketone, 1,3-hexadiene-5-one, from ethinylbutadiene and from mixtures of ethinylbutadiene and divinylacetylene.

Example 9 A flask is equipped with an agitator, a dropping funnel and a condenser set up for steam distillation.. Air in the apparatus is displaced with nitrogen and 1500 to 1600 parts by volume of crude divinylacetylene containing approximately 0.1% of hydroquinone is introduced and the agitation started. With the apparatus under a slight pressure of nitrogen to maintain oxygenfree conditions, 1250 parts by volume of the following stock solution is added to the divinylacetylene through the dropping funnel during a period of 15 to 20 minutes:

Parts Mercuric sulfate 345 Copper sulfate 30 Water 2850 96% sulfuric acid 1025 During this addition, the temperature is held below 32 C. by means of a water bath; mixing is continued for one hour, and at the end of this period, a low pressure steam jet is introduced and the volatile constituents are distilled through the condenser into a receiver swept with nitrogen and containing 1 part of hydroquinone. After approximately 1100 to 1200 parts by volume of oil with a specific gravity of 0.77-0.80 is obtained, the rate of steam distillation decreases perceptibly and a yellowish distillate begins to come over. This yellowish oil may be collected separately and will supply approximately 100 to parts by volume of crude 1,3-hexadiene-5-one, specific gravity 0.84-0.90.

Example 10 Eighty parts of ethinylbutadiene (containing 0.1% hydroquinone) prepared by liberation from the copper salt by means of alkali cyanide and distilling is slowly added to a vigorously agitated solution of 100 parts mercuric sulfate, 8 parts copper sulfate and 300 parts concentrated sulfuric acid in 800 parts of water. During the addition, the temperature is held below 50 C. Agitation is continued for one hour at this temperature under an atmosphere of nitrogen; then the volatile constituents are steam distilled into a nitrogen swept receiver containing a small amount of hydroquinone. The light water insoluble oil is separated, dried and fractionated giving a good yield of 1,3-hexadiene-5-one.

Example 11 Five parts of mercuric oxide were dissolved in 30 parts of sulfuric acid by heating and the mixture was added to a mixture of 200 parts of isopropyl alcohol and 90 parts of water. To this was added 80 parts of ethinylbutadiene under an atmosphere of nitrogen, drop by drop, during a period of 30 minutes. The reaction mixture was heated to reflux and boiled gently for three hours, after which it was steam distilled and the oily layer collected and fractionated as before to obtain the hexadieneone.

In the above examples, the success in completely removing the ethinylbutadiene in a single treatment will depend upon its concentration in the crude divinylacetylene. If the ethinylbutadiene is high, it will be necessary to repeat the hydration, or, if preferred, the relative concentration of divinylacetylene to the hydration catalyst may be reduced and the time of contact prolonged, thus accomplishing complete removal in a single treatment. The composition of the hydrating mixture is not critical. The strength of the sulfuric acid may vary between 20 and 45% in the mixture; copper sulfate need not be added, but assists in maintaining the activity of the hydration mixture; the concentration of mercury may vary from to saturation, the activity varying correspondingly, but being most eficient in the region of '7 to I have also found that a satisfactory mixture may contain potassium bisulfate in place of a part of the sulfuric acid. Catalysts capable of hydrating acetylenic compounds are essentially acid solutions of mercury salts. There are numerous well-known modifications of the basic composition, generally designed to assist in maintaining the mercury in an active state. All of these modifications are applicable in the manufacture of 1,3-hexadiene-5-one, particularly the addition of copper sulfate, for example to the extent of 0.5 to 1.5% and the addition of ferrous sulfate in comparable amounts.

Example 9 illustrates the use of an aqueous hydrating mixture and Example 11 describes a system which is essentially an organic solvent. The reaction is slow in an aqueous medium owing to the insolubility of the ethinylbutadiene, therefore it is frequently advantageous to use a mutual solvent such as an alcohol, particularly isopropyl alcohol.

In order to completely recover the 1,3-hexadiene-5-one, the steam distillation of the hydrated divinylacetylene may be continued until i the yellow oil practically ceases to come over. This oil may be vacuum fractionated to separate divinylacetylene which it contains, collecting the pure ketone at 35 to 36 C. at 5 mm. pressure (145 C. at 760 mm.).

The temperature of the hydration reaction is not critical. The rate of reaction increases with increase in temperature, but at elevated temperatures side reactions may occur, namely, oxidation by mercury salts with the precipitation of metallic mercury, and polymerization. Both of these are particularly evident when an aqueous solution is used. The reaction is generally carried out at to 100 C. and preferably at a temperature of not over 85 C. when using a solvent or 50 C. when using an aqueous system.

Ethinylbutadiene oxidizes in air to from undesirable by-products and explosive peroxides, therefore in all of its reactions, it is desirable to work under an inert atmosphere such as nitrogen, hydrogen, or methane. There is also evidence that the formation of peroxides results in deterioration of the mercury catalyst, and the life of the catalyst solution is apparently shorter if peroxides are present in the ethinylbutadiene when the reaction is started or if they are allowed to form during reaction.

As regards the polymerizaton of ethinylbutadiene, numerous and Well-known variations may be introduced, concerning principally temperature, pressure, light, catalysts, inhibitors, etc. Ethinylbutadiene may be polymerized by itself or mixed with other compounds, polymerizable or not.

The same considerations apply to the polymerization of the hydrochloride of ethinylbutadiene. Furthermore, it must be understood that the addition of hydrochloric acid to this hydrocarbon may be carried out under other conditions susceptible to yield different products. For example, in the absence of cuprous chloride, a different hydrochloride could be obtained; in the vapor phase, with other catalysts or under more drastic conditions, compounds containing 2 or more molecules of H01 per mole of hydrocarbon could be obtained.

In addition to the above described methods for separating divinylacetylene and ethinylbutadiene, it is also possible to effect a separation by precipitating the ethinylbutadiene in the form of its alkali and alkaline earth metal salts, such as its sodium or calcium salts. The precipitation is effected under anhydrous conditions but the free metals are used as the precipitants instead of their salts as in the case of copper, etc. Divinylacetylene may then be separated from the precipitated salts by filtration under oxygen-free conditions. Some ethinylbutadiene may be recovered from the alkali salts by washing the precipitate free of divinylacetylene with ether and carefully hydrolyzing with water or a Water and ethanol mixture, for example. Preferably, the precipitation of the alkali salts is carried out in the presence of an inert solvent for the divinylacetylene, such as ether or liquid ammonia. It is also possible to effect the precipitation with alkali or alkaline earth metal amides instead of the free metals.

This invention provides methods of obtaining new products from acetylene polymerization products, particularly ethinylbutadiene. Ethinylbutadiene, through its unsaturation and acetylenic hydrogen is well adapted to the synthesis of almost innumerable useful derivatives, of which a large number will polymerize as will ethinylbutadiene itself.

A good method of making 1,3-heXadiene-5-one has been discovered and this new compound has been isolated and characterized. This new compound Which is a diolefinic ketone possesses the resin forming properties of the Well-known methylene ketones such as methyl vinyl ketone, but owing to its conjugate diolefinic character, the tendency to polymerize is substantially increased. It is useful, therefore, particularly for the preparation of resins and plastics, either alone or in combination with other polymerizable compounds. It may be used also as the ketone constituent of typical phenolic-carbonyl condensation products, and owing to its unsaturation, polymerizable products result. Hexadieneone displays the characteristic properties of a diolefin and also a ketone, therefore may be used in condensations with maleic anhydride, quinones, amines, etc. for the synthesis of cyclic and heterocyclic derivatives. Its highly reactive structure permits numerous nitrogen-carbon and carboncarbon condensations, forming intermediates interesting in the synthesis of rubber chemicals, dyes and pharmaceuticals.

It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. The method of preparing 1,3-heXadiene-5- one which comprises reacting ethinylbutadiene with water in the presence of sulfuric acid and mercury sulfate.

2. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with water in the presence of sulfuric acid, mercury sulfate, and a mutual solvent for water and ethinylbutadiene.

3. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with water in the presence of sulfuric acid, mercury sulfate, and a mutual solvent for water and ethinylbutadiene of the group consisting of a1- cohols.

4. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with water in the presence of isoprop-yl alcohol as a mutual solvent and in the presence of sulfuric acid and mercury sulfate.

5. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with water in the presence of isopropyl alcohol as a solvent and in the presence of sulfuric acid and mercury sulfate, at a reaction temperature of below 85 C. and in a non-oxidizing atmosphere and separating out the 1,3-hexadiene-5-one by steam distillation.

6. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with an aqueous solution of sulfuric acid and mercuric sulfate and isolating the resulting 1,3- heXadiene-5-one.

7. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with an aqueous solution of sulfuric acid and mercuric sulfate at a temperature below 50 C. and in a non-oxidizing atmosphere and separating out the 1,3-hexadiene-5-one by steam distillation.

8. The method of preparing 1,3-hexadiene-5- one which comprises reacting ethinylbutadiene with an aqueous solution of sulfuric acid, mercuric sulfate and cupric sulfate at a temperature below 50 C. and in a non-oxidizing atmosphere and separating out the 1,3-hexadiene-5-one by steam distillation.

9. As a new compound, 1,3-heXadiene-5-one.

ALBERT S. CARTER. 

